Let's assume a situationyou are full of sweat, very thirsty and your throat is dry but you are not getting water anywhere near by. In such situation, you stand under shade of a tree to eliminate fatigue. There is a building in front of that tree. Just then a window of an apartment on first floor of building opens and person looks around. He sees you. Looking at you that person understand your situation and by gesture of hands, that person asks you if you need water. You felt relieved. At this time what will you think about that person? When you responded in yes, that person signals that he is coming down with water and closes the window. Now, door on ground floor doesn't even open after 15 minutes. What will you think about that person now? After 16 minutes door opens and man came out toward you with a bottle and says: I am sorry for delay but seeing your condition, I thought it would be best to give you lemonade instead of water, so it took sometime. Now think, your opinion about that person must have changed.. Right? Remember that you have not received any water or lemonade yet. Now, as soon as you drink that lemonade, you realize that there is no sugar in it. How do you feel about that person now? Seeing you face full of sourness, person gently bring out a pouch of sugar powder and giving it to you says: you can add as much as you want according to your taste. Now, your opinion about same person must have changed again? In a normal situation like this, if our opinion keep changing again and again, are we worthy of giving opinion on anyone. 
In fact, by seeing the world, it is understood that if a person behaves according to your expectations then he is good, otherwise he is bad. 